Erik Morales has officially been charged with anti-doping violations by the United States Anti-Doping Agency for allegedly testing positive for the banned substance clenbuterol prior to his October 2012 rematch with Danny Garcia, according to a copy of the correspondence sent to Morales by the agency and obtained by BoxingScene.com.

A USADA review board concluded that two samples taken from Morales — one on Oct. 3, another on Oct. 10 — provided “sufficient evidence of an anti-doping rule violation,” reads the letter, which is dated Feb. 8.
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Why did USADA or GBP not stop the fight from happening? Its kinda like the Commission tests where a decision comes after the fight.

Closing the stable door after the horse has bolted springs to mind

Cause they dont have to, USADA has no jurisdiction over the boxing commission and USADA is employed by the Promoter in this case it was GBP, So a Failed test has no real ramification in the boxing world other then tainting a fighters name.